Developing the 85Kr tracer gas technique for air exchange rate measurements in naturally ventilated animal buildings

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Research Paper

Developing the 85Kr tracer gas technique for air exchange rate measurements in naturally ventilated animal buildings M. Samer a,c,*, H.-J. Mu¨ller a, M. Fiedler a, C. Ammon a, M. Gla¨ser a, W. Berg a, P. Sanftleben b, R. Brunsch a a

Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Department of Engineering for Livestock Management, Max-EythAllee 100, 14469 Potsdam, Brandenburg, Germany b State Institute for Agriculture and Fishery MV, Institute of Animal Production, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany c Agricultural Engineering Department, Faculty of Agriculture, Cairo University, El-Gammaa Street, 12613 Giza, Egypt

article info

Experiments were performed to study air exchange rates (AER) occurring in naturally

Article history:

ventilated dairy buildings during summer seasons 2006 to 2010. A tracer gas technique (TG)

Received 11 February 2011

for AER measurements was developed. The AERs were determined by decay of radioactive

Received in revised form

tracer Krypton-85, and CO2-balance used as the reference method (RM). During each

12 April 2011

experiment, continuous measurements of gaseous concentrations (NH3, CO2, CH4 and N2O)

Accepted 21 April 2011

inside and outside the building and

Published online 25 May 2011

combined factors investigated were release over feeding table (a1) or over the manure alley

85

Kr tracer gas experiments were performed. The

(a2), average a-values (b1) or the sum of impulses (b2), selected radiation counts (c1) or all radiation counts (c2). The results were compared using Pearson correlation analysis, developing a linear regression model, and testing the differences between the factor combinations and the RM using an ANOVA model. There were differences between impulses (Pr > jtj ¼ 0.0013), where the sum of impulses showed better results than the average a-values. Although there was no difference (Pr > jtj ¼ 0.344) between the readings of the radiation counts, it was considered that by using all the readings of the radiation counters it was more representative and easier to calculate the AER. The best factor combinations, having the highest coefficient of determination values R2, and the most reliable parameter estimates, were: a1b2c2 (R2 ¼ 0.94; 1.63  0.14); and a1b1c1 (R2 ¼ 0.97; 2.03  0.11). The gaseous emissions, subject to the RM, were 3.9, 19, 1656, and 0.96 g h1 AU1 (AU is animal unit of 500 kg) for NH3, CH4, CO2 and N2O respectively. ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved.

Abbreviations: a, release location; a1, 85Kr released over feeding table; a2, 85Kr released over manure alley; AER, Air exchange rates; ANOVA, Analysis of variance; AU, Animal unit of 500 kg; b, Implementation of impulses; b1, Average a-values; b2, Sum impulses; Bq, Becquerel; c, revision of radiation counters; c1, Selected radiation counters; c2, All radiation counters; GBq, Giga Becquerel; hpu, Heat production unit; MeV, Mega electron volt; MP, Gas sampling point; RM, Reference method; TG, Tracer gas technique; TFL, Temperaturehumidity logger; Z, radiation counter. * Corresponding author. Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Department of Engineering for Livestock Management, Max-Eyth-Allee 100, 14469 Potsdam, Brandenburg, Germany. Tel.: þ49 (0) 331 5699 518; fax: þ49 (0) 331 5699 849. E-mail addresses: [email protected], [email protected] (M. Samer). 1537-5110/$ e see front matter ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2011.04.008

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Nomenclature

QR

Symbols ai bj Ci ck Co eijkl F I

QTG

I0 KCO2 m n P

1.

fixed effect of release location fixed effect of implementation of impulses gas concentration inside the building, (mg m3) fixed effect of revision of radiation counters gas concentration outside the building, (mg m3) random residual temperature correction factor impulses recorded by the radiation counters per second, (impulse s1) impulses recorded by the radiation counters impulses at t ¼ 0, (impulse s1) excretion rate of CO2 from one cow, (mg h1 cow1) average mass of the animals, (kg cow1) number of cows housed inside the building days after insemination, (day)

Introduction

The quantification of gaseous emissions from livestock buildings with natural ventilation systems is a particularly difficult task and is associated with uncertainties which are largely unknown. One key issue is to measure the air exchange rate (AER), to calculate the ventilation rate and then to quantify the gaseous emissions. Measurements of NH3 emission, especially from cattle buildings, are needed to assess the environmental impact of ammonia. Furthermore, greenhouse gases such as CH4 and N2O are also relevant due to their global warming potentials. Natural ventilation is a more energy efficient approach to provide effective ventilation and this technique is gaining in interest. The major problem of natural ventilation is the lack of accurate, continuous and online measuring and controlling techniques for AERs, which is crucial for monitoring emissions from buildings and for control of indoor air quality (Van Buggenhout et al., 2009). Natural ventilation of buildings is generated from two distinct sources; buoyancy or gravity effects due in large part to temperature differences between the outside and the inside air; wind blowing over a building, generating pressures and suctions at different points, forcing air in and out of the building (Sallvik, 1999). Unfortunately, the quantification of the gaseous emissions from naturally ventilated animal houses is complex and exhibits large uncertainties; particularly in the determination of ventilation rates. Therefore, methods to determine AERs need to be improved and further developed (Amon & Fro¨hlich, 2006; Hatem, 1993; Keck, Schrade, & Za¨hner, 2006; Monteny, 2000; Mu¨ller, Krause, & Grimm, 2001). The flux of emissions of harmful gases from naturally ventilated buildings is dependent on wind velocity (both speed and direction) and turbulence levels inside and over the outside of the building, thus emission mass flow is highly variable and difficult to estimate (Hatem, 1993; Hellickson & Walker, 1983; Ngwabie, Jeppsson, Nimmermark, Swensson, & Gustafsson, 2009; Van Buggenhout et al., 2009). The factors-of-influence (FOI) that

t Ti Y yijkl a n m FCOR: FLM FMY FP Ft

277

ventilation rate calculated according to CO2balance, (m3 h1) ventilation rate estimated using the tracer gas technique, (m3 h1) time, (s) temperature inside the barn, ( C) milk yield, (kg d1) difference of the air exchange rate to the reference method air exchange rate per second, (s1) volume of the building, (m3) general mean difference of the air exchange rate to the reference method corrected value of the total heat production, (W) required heat production for life maintenance, (W) required energy for milk yield, (W) required energy for pregnancy, (W) total heat production, (W)

strongly influence the dispersion of NH3 are: NH3-mass-flow, internal and external temperatures, mean and turbulent wind components in horizontal and vertical directions, atmospheric stability, and exhaust air height where the continuous measurement of NH3 remains a challenging and costly enterprise, in terms of capital investment, running costs or both (Von Bobrutzki et al., 2010; Von Bobrutzki, Mu¨ller, & Scherer, 2011). In order to determine ventilation rates in such cases, many approaches are available. For measuring the AERs and to calculate the emission streams a special tracer gas method has been developed (Mu¨ller & Mo¨ller, 1998). Tracer gases may include the radioactive isotope krypton-85 (Lung, Mu¨ller, Gla¨ser, & Mo¨ller, 2002; Mu¨ller & Mo¨ller, 1998), CO2 (Kittas, Boulard, Mermier, & Papadakis, 1996), tetrahydrothiophene C4H8S (Lung et al., 2002), perfluorocarbon (Okuyama, Onishi, Tanabe, & Kashihara, 2009) or sulphur hexafluoride SF6 (Pinares-Patino & Clark, 2008; Scholtens, Dore, Jones, Lee, & Phillips, 2004; Snell, Seipelt, & van den Weghe, 2003). On the other hand, measurements of multizone ventilation rates can be performed using tracer gas techniques (TGs) whereas tracer gases are able to treat multiple zones, e.g. complex buildings in which there are sub-sections that can be isolated. Multizone techniques recognise that not only does airflow between the investigated building and the outside, but that there are airflows between different parts, or zones, inside buildings and multizone techniques are able to measure these flows (Okuyama et al., 2009; Sherman, 1989). Tracer gases are used for wide variety of detection techniques including atmospheric tracing and leak detection (Gla¨ser, Klich, & Creifelds, 1986). Additionally, the TG is one of the approaches used for quantifying ventilation rates in naturally ventilated buildings which including the measurement of infiltration, air exchange, and the dispersion of pollutants. According to ASABE Standards (2008) infiltration is uncontrolled air exchange which occurs through small, uncontrolled openings in building coverings, such as gaps around doorways, utility service entrances and

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between covered sections. These exchanges are driven by wind pressure and/or temperature differentials between inside and outside the building. A very important aspect of the TG is the possibility to testing occupied buildings. This is not only more convenient but it is also more accurate since it takes into consideration the significant effects of occupancy on the ventilation rate, and the effects of opening and closing doors and windows which occurs during normal working conditions and in most cases is significant. The four known tracer gas injection methods are: (1) constant tracer gas injection, (2) variable tracer gas injection, (3) fan duct constant flow, and (4) concentration decay (Brehme, 2000; Mu¨ller & Mo¨ller, 1998; Schneider, Buscher, & Wallenfang, 2005). Demmers et al. (2001) stated that the constant release tracer gas method gives the more reliable estimates of ventilation rate. Brehme (2000) described the compartmentalisation method which was used for many measurements in dairy buildings. This tracer gas method (i.e. decay method) combines, through a dispersion mechanism, concentration measurements with air exchange measurements within which the volumetric flow rates are permanently fluctuating. The dependency of NH3 emission mass flow has been derived in form of mathematical model as well as measured data or values. Generally, the variation of tracer gas concentration with time and space defines the total and local ventilation rates, ventilation effectiveness, and gas distribution in the investigated building. This technique is based on the assumption of complete mixing of tracer gas with air within the building. However, in practice, completely mixed air spaces are rarely found in naturally ventilated buildings and it is difficult to achieve uniform distribution of the tracer gas within the space (Barber & Ogilvie, 1982). The most convenient method for using 85Kr in animal buildings is therefore concentration decay, where owing to the risk of the radioactivity, building size, environmental requirements, and costs using mixing ventilators is recommended. Furthermore, the decay method requires a limited amount of tracer gas (Mu¨ller & Mo¨ller, 1998). Ponchant et al. (2008) reported among the three methods: estimating of heat losses and gains, determining of air loss using a tracer gas, and measuring of gas concentrations in the air and in manure (CO2, CH4, NH3, NO2 and water vapour) the best measurement was measuring gas concentrations. Xin et al. (2009) compared indirect ventilation rate measurement through CO2-balance to the direct measurement method by continuously monitoring the operation of in-situ calibrated exhaust fans which is an exact and accurate method. Their results showed no significant differences between both direct and indirect methods. They added that the CO2-balance or concentration difference method offers a viable alternative or supplemental check for quantifying building ventilation rates under conditions where direct, continuous ventilation rate measurement is not feasible. According to Pedersen et al. (1998), the use of the CO2-balance is a reliable method to estimate the ventilation rate for non-insulated livestock buildings, where only small differences between inside and outside temperatures occur which is the case of the building investigated in our study. Madsen, Bjerg, Hvelplund, Weisbjerg, and Lund (2010) stated that a simple, fast, reliable and cheap method to estimate the production of gases from animals is using the carbon dioxide (CO2) concentrations in air near the

animals combined with an estimation of the total CO2 production from information on the intake of metabolic energy or heat producing units. However, the CO2-balance method has several error sources such as: calculating metabolic energy, CO2 produced per energy unit, the amount of CO2 emitted from manure and the location of CO2 sampling points. The TG could be further developed to the point where it delivers comparable results and is independent from the physiological changes. In contrast, the CO2-balance method depends on animal production of CO2 which varies with animal weight, productivity and pregnancy. The determination of ventilation rates from naturally ventilated buildings is a key factor in quantifying emission flow rates from animal buildings. There is a need to improve the accuracy of ventilation rate measurements, where no accurate, reliable, and online method is available for ventilation rate measurement in naturally ventilated livestock buildings. Therefore, the objective of this study was to evaluate and develop the 85Kr TG and compare the ventilation rates measured by the decay of the radioactive tracer isotope 85 Kr with those obtained by the CO2-balance which was set as the reference method (RM).

2.

Materials and methods

2.1.

Site description

The measurements were carried out during summer seasons of 2006e2010, in a naturally ventilated dairy buildings (Fig. 1) located in Dummerstorf, Mecklenburg-Vorpommern, northeast Germany (217 km north-west Berlin, at latitude of 54 10 000 N, longitude of 12 130 6000 E, and at an altitude of 43 m). Fig. 2 shows the farmstead layout where the investigated building is surrounded by several other agricultural buildings, except along the southern and western sides. Fortunately, the prevailing summer winds are from the south and south-west. The dairy building was 96.15 m long and 34.2 m wide. The roof height varied from 4.2 m at the sides to 10.73 m at the gable. The internal volume of the building was to 25,499 m3. It was designed to accommodate 364 dairy cows in loose housing system with freestalls (i.e. 70 m3 cow1). The manure handling system was equipped with winch-drawn dung channel scrapper. The dairy building was naturally ventilated by air introduced into the building through adjustable curtains in the sidewalls (which were protected by nets), open ridge slots, space boards of the gable walls, and open doors in the gable walls. During the summer season, three additional ceiling fans were used to enhance the uniformity of air distribution inside the barn. The fans were mounted from the ceiling along the centreline of the building 5 m above floor. Each fan had a diameter of 7.2 m with a maximum discharge of 546,000 m3 h1.

2.2.

General procedures

Measurements were conducted throughout different summer seasons over 2-week period per season, where wind velocity and air temperature inside and outside the building were recorded. Concentrations of carbon dioxide (CO2), ammonia

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279

Fig. 1 e Investigated dairy barn.

(NH3), methane (CH4), and nitrous oxide (N2O) were continuously measured inside the barn at eight uniformly distributed points and outside the barn at four points (Figs. 3 and 4). Within the aforementioned periods, ventilation measurements were carried out using the tracer radioactive isotope Krypton-85. The tracer gas was released inside the building in order to determine the AER using the decay method and AERs were determined by the RM. The emission mass flow rate from the livestock building was calculated as the product of the concentration difference between emitted and fresh air and the airflow rate derived by the RM. Measurements of temperature and relative humidity were carried every minute out using sensors (Comark Diligence EV N2003, Comark Limited, Hertfordshire, England) positioned at four locations inside the building and 2 locations outside (Figs. 3 and 4). Ambient wind conditions were measured by means of a weather station (DALOS 515c-M, F&C Forschungstechnik & Computersysteme GmbH, Gu¨lzow, Germany) located near the dairy building. Local wind and turbulence quantities of all three velocity components were sampled at a frequency of 1 Hz. Gas concentrations were measured using an infrared photo-acoustic analyser (INNOVA 1312, Innova AirTech Instruments, Ballerup, Denmark) with 12 sampling points. The concentration measurements took place in a continuous sequence. As a result each sampling point was assessed at intervals of about 12 min (w1 min per sampling point). Twenty radiation counters (LB 6357, Berthold Technologies GmbH & Co KG, Bad Wildbad, Germany) were distributed inside the barn to count the radioactive impulses of 85Kr. Table 1 gives an overview of all measurements carried out inside and outside the dairy building. Figs. 3 and 4 show the design of the investigated dairy barn and the different measuring points, where the triangles designate 85 Kr detection points or radiation counters (Z) which were placed

at a height of 3.2 m from the floor (i.e. the manure alley). The red squares indicate gas sampling points (MP) and the blue squares show the temperature-humidity sensors (TFL), where both were placed at a height of 2.9 m. The dashed orange line and the cross represent gas distribution line which was at a height of 1.60 m approximately. The tracer gas was released over the southern manure alley and the middle of the building along the feeding line. The external gas sampling point (MP4) and temperaturehumidity logger (TFL 11) were placed 11 m south of the barn (36.7 m from the eastern side of the building) in order to measure the external temperature and relative humidity, and to sample the gases from fresh external air as a reference. The other external temperature and humidity logger (TFL10) was mounted on the northern wall of the barn, and the external gas sampling point (MP7) was located 3 m north of the barn.

2.3.

Measurements of ventilation rates

The parameters required by the ventilation methods were measured simultaneously in order to allow direct comparison between the methods. The impact of radioactive isotope 85Kr on the environment, workers and cows was also investigated.

2.3.1.

CO2-Balance

Carbon dioxide, formed by animal respiration, can be used as a natural tracer gas. The ventilation rate throughout the building can be determined by calculating the mass balance of CO2 flow. CO2-balance is not in general terms used a RM to measure AERs. However, it was used as a reference in this study because direct comparison with other more accurate methods was not possible. The CO2-balance and the CO2 excretion calculations are based on heat and CO2 excretion models and the results of several studies (Albright, 1990; CIGR, 1984; CIGR, 2002; DIN 18910-1, 2004; Hellickson & Walker, 1983).

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Fig. 2 e Farmstead layout, where (1) another dairy barn, (2) milking parlour, (3) open field, (4) manure tanks, (5) young-stock housing, (6) workshop, (7) administration, and (8) forage storage buildings.

Equation (1) describes the relationship between the ventilation rate and the gas production rate assuming ideal mixing with the air inside the building: QR ¼ n,KCO2 ,ðCi  Co Þ1

(1)

Where, KCO2 (mg h1 cow1) represents the excretion rate of CO2 from one cow, n is the number of cows housed inside the building, QR (m3 h1) is the ventilation rate calculated according to the RM, i.e. CO2-balance, and Ci (mg m3) and Co

(mg m3) are the concentrations of the gas inside and outside the building, respectively. The AER can be then calculated by dividing the ventilation rate by the volume of the building. However, the gas concentration inside the building is not the uniform and varies with time; therefore Eq. (1) is only an approximate estimate for gas production in dairy buildings. Within the CO2-balance, CO2 excretion rate depends on heat production. Hence, the CO2 excretion rate can be calculated as follows (Albright, 1990; Hellickson & Walker, 1983):

Fig. 3 e Plan view of the investigated barn. Where, MP labels gas sampling point, Z indicates radiation counter, and TFL shows temperature-humidity sensor. The dark grey areas represent the freestalls, and the light grey area represents the feeding table.

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Fig. 4 e Side view of the investigated dairy barn. Where, MP labels gas sampling point, Z indicates radiation counter, and TFL shows temperature-humidity sensor.

FLM ¼ 5:6ðmÞ0:75

(2)

FP ¼ 1:6  105 ðPÞ3

(3)

FMY ¼ 22,Y

(4)

Ft ¼ FLM þ FP þ FMY

(5)

Ft ¼ 5:6ðmÞ0:75 þ1:6  105 ðPÞ3 þ22Y

(6)

The CO2-balance has some sources of inaccuracy, for example; the use of computation models for metabolic energy, the amount of CO2 produced per energy unit, the quantity of CO2 produced emitted from manure, variations of ambient temperatures and the location of CO2 measuring points. Unfortunately, CO2-balance depends on the animals producing CO2 which varies as a function of milk yield, animal weight and pregnancy. On the other hand, the tracer gas measurements deliver comparable results but independent from the physiological changes.

FCOR: ¼ Ft ,F

(7)

2.3.2.

F ¼ 4  105 ð20  Ti Þ3 þ1

(8)

KCO2 ¼ 0:299,FCOR

(9)

Where, FLM (W) represents the required heat production for life maintenance, FMY (W) is the required energy for milk yield, and FP (W) designates the required energy for pregnancy. On the other side, Ft (W) represents the total heat production, and FCOR: (W) is the corrected value of the total heat production. Additionally, several parameters were considered where m (kg cow1) represents the average mass of the animals, P (day) is days after insemination, Y (kg d1) designates the milk yield, Ti ( C) represents the temperature inside the barn, and F is the temperature correction factor. In Eq. (9), the unit of KCO2 is in g h1 cow1 which should be converted to mg h1 cow1 in order to substitute resulted value into Eq. (1).

Table 1 e Measured aerodynamic and microclimatic parameters inside the building. Year Total experiments

2006

2007

2008

2010

4

3

2

5

Experiment 1 2 3 4 1 2 3 1 2 1 2 3 4 5 Number of 18 20 radiation counters (all) Number of 5 2 9 8 10 16 17 18 18 16 7 16 19 15 radiation counters (selected) Number of 6 temperaturehumidity sensor/loggers Number of multi12 gas-monitor measuring points

Tracer gas technique

Krypton-85 was distributed four to five times each summer season. There were twenty two summer experiments but 14 were considered because 8 were used to develop procedures and methods. Gas was released inside the building and ideal mixing of both the air and tracer gas inside the building was assumed. The duration of each tracer gas measurement was 10 min including the release, decay and idle time. During the two week periods when the gaseous concentration was measured, temperature and relative humidity were continuously measured. The tracer gas experiments were conducted in the middle of the 2-week period of each set of measurements. Tracer gas was constantly released during each investigation and the decrease of impulses was measured for each release. The quantity of the released 85Kr was 2 GBq per experiment. Tracer gas was released as a line source along the feeding line located at the centre of the building and in a line over the southern manure alley which was orthogonal to the prevailing summer winds (south and south-westerly) allowing for better mixing of 85Kr in air that intrudes into the building. The manure alley was only 2.5 m from the side of the building and the curtains were open as according to the usual procedure in the summer season. Additionally, the ventilator fans were in operation in order to assure a better mixing of 85Kr with the air. Twenty radiation counters, with a counting rate of 1 Hz, were uniformly distributed across the whole area of the cowshed at a height of 3.20 m (Figs. 3 and 4). Uncertainties with this method can be caused by inadequate mixing of the tracer gas in the air plenum of the building. The ventilation rate was calculated using the decay method of radioactive 85Kr as follows: I ¼ I0 ,ea,t

(10)

QTG ¼ a,n

(11)

Equation (10) is an exponential function, where I represents the impulses recorded by the radiation counters per second, t is the time in seconds, a (s1) represents the AER per second,

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and I0 is the impulses at t ¼ 0 (Gla¨ser et al., 1986). The term a (s1) should be converted to AER per hour in order to be used in Eq. (11) where, n (m3) is the volume of the building, and QTG (m3 h1) represents the ventilation rate estimated using the TG. Calculation procedures were compared. They were: (1) average a-values of selected radiation counters, (2) average a-values of all radiation counters, (3) sum impulses of selected radiation counters, and (4) sum impulses of all radiation counters for both release locations manure alley and feeding table. Fourteen tracer gas experiments were carried out, each including 2 release locations. Because four calculation procedures were compared, a total of 56 AER values were statistically analysed.

3.2.

2.4.

3.3.

Statistical analysis

The aim of the statistical analysis was to comprehensively evaluate the relationship between the eight procedures (four procedures of AER calculation and two release locations). The eight procedures were factor combinations among release over feeding table (a1) or over manure alley (a2), average a-values (b1) or sum impulses (b2), selected radiation counters (c1) or all radiation counters (c2). Pearson correlation analysis was performed to test a linear relationship between the AERs estimated by the eight procedures. Additionally, a linear regression model without an intercept was used to study the relationship between the RM, i.e. CO2-balance, and the eight procedures. Furthermore, the differences between the RM and the eight procedures were tested using an ANOVA model. ANOVA can determine factors of influence on an observed trait. In this case the observed trait was difference of AER calculated for the tracer gas method (in different factor combinations) to the RM and the factors were (a) release location, (b) implementation of impulses (calculation method) and (c) revision of radiation counters. Estimated values for the factor levels can give an idea about the combinations of factors that provide minimal differences when compared to the RM, hence suggesting this factor combination for further improvement of the method. The hypothesis of the ANOVA model was that there is no effect of factors a, b and c at a significance level of a ¼ 0.05. This leads to the following linear model: yijkl ¼ m þ ai þ bj þ ck þ eijkl , where yijkl represents the difference of the AER to the RM; m is the general mean difference of the AER to the RM; ai , bj , and ck are the fixed effects of the aforementioned factors; and eijkl represents the random residual. The statistical analysis was carried out using SAS v.9.2 (SAS Institute, Cary, NC, USA).

3.

Results

3.1.

Climatic conditions

The temperature outside the barn ranged from 14.5  C to 29.3  C during the investigations. The temperature inside the building ranged between 15.3  C and 31.4  C. The wind velocity (direction and speed) fluctuated, with wind direction ranging from 116 to 359 from north and the wind speed varying from 0.4 to 3.64 m s1.

Air exchange rates

The 56 AER values were statistically analysed. Table 2 shows the results of the correlation analysis, Table 3 shows the results of the regression analysis, and Table 4 shows of the ANOVA model. Fig. 5 shows the differences of AERs of the eight tracer release procedures to the RM. An important observation was that all radiation counters detected the tracer gas when it was released over the manure alley compared to a maximum of 15 radiation counters detecting the tracer gas when it was released over the feeding table. Table 5 summarises the AERs for the two studied techniques, the ventilation rates and the gaseous concentrations.

Gaseous emissions

The gaseous emissions, subject to the RM, were 3.9, 19, 1656, and 0.96 g h1 AU1 for NH3, CH4, CO2, and N2O respectively. The emission factors, subject to the RM, were 33.8, 166.6, 14504, and 8.4 kg yr1 AU1 (AU is animal unit of 500 kg) for NH3, CH4, CO2, and N2O respectively. This assumes that values from the summer measurements are representative for the whole year. Additionally, the ammonia emission factor was 46.2 kg yr1 cow1 and the ammonia emission was an average of 92.6 g d1 AU1 for the summer seasons considered.

3.4.

Environmental impact of

85

Kr

The radioactive krypton isotope (85Kr) is a nearly a pure beta radiation emitter, where 99.3% of all decays will be transformed directly into the inactive rubidium (85Rb) by emitting beta particles with a half-life of 10.27 years. Only the remaining 0.7% of decay is accompanied by gamma ray emission. The maximum energy of beta particles is 0.672 MeV, and gamma quantum of 0.513 MeV. This means that the beta radiation is completely absorbed if covered by a few millimetres thick metal sheet, e.g. a steel cylinder (Gla¨ser et al., 1986). Owing to the low level of gamma radiation, the gamma dose rate outside the shielded 85Kr is reasonably low, so that other screening means can be used during transportation, and use of 85Kr in ventilation rate measurements

Table 2 e Results of the correlation analysis. a

b

c

Pearson Correlation Coefficient

Prob > jrj under H0: Rho ¼ 0

1 1 1 1 2 2 2 2

1 1 2 2 1 1 2 2

1 2 1 2 1 2 1 2

0.94882 0.23640 0.71139 0.89334 0.23410 0.00092 0.12397 0.10403

<0.0001 0.5108 0.0211 0.0005 0.7659 0.9991 0.8760 0.8960

a1: 85Kr released over feeding table; b1: Average a-values; c1: Selected radiation counters a2: 85Kr released over manure alley; b2: Sum impulses; c2: All radiation counters.

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Table 3 e Results of the regression analysis. a b c 1 1 1 1 2 2 2 2

1 1 2 2 1 1 2 2

1 2 1 2 1 2 1 2

R2 0.97 0.44 0.86 0.94 0.72 0.66 0.57 0.54

DF Parameter Standard t Value Pr > jtj Estimate Error 1 1 1 1 1 1 1 1

2.03 3.84 1.85 1.63 4.96 5.06 1.49 1.36

0.11 1.45 0.21 0.14 1.77 2.11 0.75 0.72

18.08 2.66 7.58 11.51 2.80 2.40 2.00 1.88

<0.0001 0.027 <0.0001 <0.0001 0.067 0.096 0.139 0.156

a1: 85Kr released over feeding table; b1: Average a-values; c1: Selected radiation counters. a2: 85Kr released over manure alley; b2: Sum impulses; c2: All radiation counters.

(Gla¨ser et al., 1986). The experiments were carried out according to the permission of the Brandenburg State Office for Work Safety and Health. Tracer gases did not form other chemical compounds during the ventilation rate measurements in a similar manner to their inactive isotopes which are present in the nature under normal conditions. Animals encounter radioactivity stress. However, the fur and leather skin of the animal are able to absorb the beta radiation of 85Kr almost completely, except for the respiratory system which is exposed to radiation stress through respiration. The average volume of the respiratory system of a dairy cow is 0.005 m3 and this has the ability of absorbing 10% of the radioactivity taking into consideration that the natural radioactivity of meat is 100 Bq kg1 (LLBB, 2005). The ampoule used in each experiment contained 2 GBq, and the internal room volume of the barn is 25,499 m3 resulting in 78434.5 Bq m3. A cow inhales 0.005 m3 per breath (considering 60 breaths min1), and the peak of 85Kr concentration lasts 2 min. Hence, a cow receives a total of 4706 Bq of which 10% are absorbed making the mass-related negligible and below the detectable value of 0.724 Bq kg1 since one cow weighed 684 kg on average. Thus the additional radioactivity was below the natural radioactivity range. Similarly, workers who may need to spend a short time during the running of a test in a selected area are largely

Table 4 e Solution for fixed effects from the ANOVA model. Effect

Estimate

Standard Error

DF

Intercept b1 b2 a1 a2 c2 c1

86.9930 95.8336 0 104.91 0 26.9629 0

33.1291 28.2526

52 52 . 52 . 52 .

. 31.2699 . 28.2526 .

t Value

Pr > jtj

2.63 3.39 .

0.0113 0.0013 .

3.35 .

0.0015 .

0.95 .

0.3443 .

a1: 85Kr released over feeding table; b1: Average a-values; c1: Selected radiation counters. a2: 85Kr released over manure alley; b2: Sum impulses; c2: All radiation counters.

Fig. 5 e Differences of air exchange rates of the eight factor combinations to the reference method.

protected by their clothes against the beta radiation with only the bare parts of the body and the lungs are exposed to the radiation, where this load is negligible. Adults have natural “internal” radiation activity levels of 9000e10,000 Bq (BfS, 1993). This is mainly because that the body naturally contains the radioactive isotope 40K and 14C which react throughout the body and have higher energy compared to the beta radiation of 85Kr (40K: 1.33 MeV; 85Kr: 0.67 MeV). Under the same conditions, and considering that the air content of the lungs is 0.0015 m3 with a maximum of 20 breaths min1 (VEB, 1972), an amount of 470.6 Bq is calculated which is still under the level of natural internal radioactivity.

4.

Discussion

Although the CO2-balance method has several error sources, it was used as the RM in this study primarily because of the statements of Madsen et al. (2010), Xin et al. (2009), Ponchant et al. (2008), and Pedersen et al. (1998) who stated that the CO2balance is a reliable, simple, fast, and cheap method to estimate the ventilation rates and the gaseous emissions from animal housing. Furthermore, Xin et al. (2009) compared the CO2-balance to the direct measurement by continuously monitoring operation of the in-situ calibrated exhaust fans which is the exact and accurate method. The results showed no significant differences between both methods. The CO2balance used here was based on the calculations of CO2 excretion rate taking into consideration the internal and external CO2 concentrations. Thus, the estimated volumetric flow rate depends on the accuracy of CO2 production model in addition to other factors, e.g. weather conditions. Most of CO2 is formed by the animals and exhaled by respiration. It can also be part of exhaust gases of heating systems being

284

b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 7 6 e2 8 7

Table 5 e Air exchange rates, ventilation rates and gaseous concentrations. Experiment Release Reference over ventilation rate (m3h1)

2010e1 2010e2 2010e3 2010e4 2010e5 2008e1 2008e2 2007e1 2007e2 2007e3 2006e1 2006e2 2006e3 2006e4

Manure alley

Feeding table

2284899 580671 1052656 1305990 1502426 759882 466357 1364022 652893 912893 1260324 680660 488934 514159

Air exchange rates (AER)

Average gas concentrations

Reference Average/ Average/ Sum/ Sum/ [CO2] selected all selected all [85Kr] [85Kr] [85Kr] [85Kr] 89.61 22.77 41.28 51.22 58.92 29.8 18.29 53.49 25.6 35.8 49.43 26.69 19.17 20.16

241.74 261.79 185.76 583.92 98.86 43.34 34.2 109.37 59.28 65.54 393.88 510.96 32.16 17.04

265.5 168.69 198.68 546.82 131.81 43.34 34.2 120.31 71.136 69.91 89.2 49.9 34.7 20.9

released in the barns, which is not the case with the building investigated. Additionally, a certain portion of CO2 is released by the manure. The CO2 released from urine and dung in stored manure is less than 5% of the amount produced by respiration (Aarnink, van Quwerkerk, & Verstegen, 1992; Schneider, 1988). Concerning the uncertainties in measuring CO2 concentrations and ventilation rates, CO2 production from the urine and dung was neglected in the mass balance models. The calculations of CO2 excretion rate (g h1 cow1) were performed using the heat and CO2 production mathematical model (Eqs. 2e9). The calculations took into consideration the required energy for milk yield, the required energy for pregnancy, and the heat production for life maintenance where the average mass of the animals was considered. These procedures agree with Pedersen et al. (2008) who mentioned that although over the last decade a fixed carbon dioxide production of 185 l h1 per heat production unit, hpu (i.e. 1000 W of the total animal heat production at 20  C) has often been used, but the CO2 production per hpu increases with increased body mass. Furthermore, the implemented method in our study agrees with Madsen et al. (2010) who stated that the CO2 excretion can be calculated from the intake of metabolic energy and the energy in the weight gain or milk produced, as there is close relation between heat production and CO2 excretion. The gaseous concentrations varied as a function of time of measurement and the location of the sampling point inside the dairy building. Therefore, the measurements were carried out over 2 weeks whereas the eight sampling points were symmetrically distributed inside the building to cover the whole area of the barn (Figs. 3 and 4). Both concepts and procedures agreed with those stated and performed by Ngwabie et al. (2009). The constant release tracer gas method was implemented mainly because of the work of Demmers et al. (2001) who validated the release of tracer gas in a full-scale cross-section

64.44 42.48 185.04 60.84 79.2 24.84 26.62 106.2 51.12 75.6 97.2 28.8 20.16 18.36

75.6 58.32 192.96 61.2 83.16 24.84 26.62 50.4 54 61.2 129.6 61.2 21.6 18

CO2

978.57 914.27 824.36 794.13 772.58 858.22 989.21 977.83 986.03 888.83 787.04 903.74 1003.24 985.90

 186.11  35.71  132.18  84.40  53.78  118.60  158.93  190.39  160.62  82.52  166.23  274.43  193.78  284.09

NH3

CH4

N2O

4.05  1.38 3.94  1.91 2.20  0.84 1.55  0.44 2.15  0.93 1.85  1.32 2.88  0.90 2.11  0.30 2.50  0.87 2.03  0.57 1.00  0.97 1.82  2.07 2.51  1.20 2.69  2.02

13.06  6.57 11.27  2.54 9.90  4.62 8.19  2.57 8.29  3.07 10.77  5.12 15.63  5.89 11.47  4.20 13.69  6.58 8.81  1.73 5.35  8.28 9.27  11.35 12.23  6.58 12.93  10.02

0.64  0.04 0.66  0.07 0.56  0.04 0.57  0.07 0.60  0.04 0.43  0.04 0.44  0.03 0.51  0.02 0.52  0.04 0.54  0.04 0.52  0.02 0.51  0.03 0.49  0.03 0.49  0.04

of a naturally ventilated livestock building against a known release rate of a gaseous pollutant at high and low wind speeds. They found a good correlation between the measured and the actual release rates for the tracer gas method. They added that the constant release tracer gas method gave the most reliable estimates of ventilation rate. In our study, the dosing of 85Kr was in a line source over the southern manure alley and this was compared to release over the feeding line. The southern manure alley was selected because it faces the prevailing summer winds, which blow from the south and south-west, and it was near (2.5 m) to the southern side of the building where the air intrudes allowing better 85Kr mixing with incoming air and better distribution throughout the whole building leading to higher 85Kr detection. This was confirmed by measurements detected all 20 radiation counters in comparison the maximum of 15 when the dosing of the tracer gas was located over the feeding line in the middle of the building. This concept also agrees with that developed by Snell et al. (2003) but in that they performed the experiments in a closed building having eaves and ridges, and sides that were closed by walls. In this study the sidewalls were open and covered by pierced nets. The correlation analysis showed that only three out of the eight factor combinations were positively correlated with the RM, and they were: a1b1c1, a1b2c1, and a1b2c2 with correlation coefficients of 0.95, 0.71, and 0.89 respectively. On the other hand, the regression analysis showed that there were no slopes that were significantly different to zero with all the manure alley based combinations. Thus this release location showed more detectability of tracer gas using the radiation counters emphasising the better mixing of tracer gas with air. This suggests that more experiments are required in order to verify this unexpected result. All combinations with releases at the feeding table showed a positive slope that was significantly different to zero. The results showed that the combinations a1b2c2 and a1b1c1 are the best combinations, having the highest correlations and the most reliable parameter estimates. The

b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 7 6 e2 8 7

ANOVA model showed no difference between the revisions of radiation counters (Pr > jtj ¼ 0.344), but showed differences between implementations of impulses (Pr > jtj ¼ 0.0013) and between the release locations (Pr > jtj ¼ 0.0015). Considering the use of impulses, the average use of impulses led to higher deviation by about 96 (h1) compared to the sum of impulses. Releases over the feeding table led to a difference in AER of about 105 (h1), lower than the release over the manure alley, and lower than the RM by 18 (h1), whilst the release over the manure alley was greater than the RM by 87(h1). This can be explained using the results of a study carried out by Mosquera, Monteny, and Erisman (2005) who stated that the flow distortion by the surrounding buildings and obstacles makes the application of trace gas technique not always exact, which is the case of the building used in our study (Fig. 2). These deviations can be attributed to the fact that there are airflows between the different sections (i.e. zones) inside the building (Okuyama et al., 2009; Sherman, 1989). In other words, tracer gas flows from one zone to another within the building and is then detected by several radiation counters leading to multidetection of the same dosing of tracer gas thereby overestimating the AER between the building and the outside. Furthermore, the deviations were also related to the permeation rate (PR), where Pinares-Patino and Clark (2008) emphasised that using a narrow range in PR and balancing of PR between treatments should be practised. This concept was considered in our study whereas all 85Kr experiments were performed using a fixed quantity; 2 GBq per experiment. However, the PR not only depends on the dose of tracer gas, but also on the airflow patterns inside the barn which varies as a function of time and location, and occupancy of the building. Therefore, the balancing of PR between treatments is difficult to achieve in naturally ventilated buildings. Van Buggenhout et al. (2009) performed tracer gas experiments for ventilation rate measurements in a laboratory test installation with an accurate RM to demonstrate the apparent difficulties of non-perfect mixing and large variations in ventilation rates which are dependent on sampling positions. Their results showed that measurement errors can be as large as 86% of the ventilation rate measured using the decay method. Overall the best position for tracer gas sampling was by the outlet, which gave measurement errors that were <10% of the reference value. Furthermore, they indicated the urgent need for a direct accurate measurement technique that makes it possible to quantify the ventilation rates for natural ventilated buildings. In our study, full-scale experiments for ventilation rate measurements using 85Kr tracer gas were carried out in a working dairy building in order to further develop the ventilation rate measurements using TG. The results of our study showed that the measurement errors were larger, which can be attributed to the fact that Van Buggenhout et al. (2009) used a mechanically ventilated test installation in laboratory which allowed accurate measurements of the ventilation rate. It was not possible to implement similar procedure in our full-scale experiments which were performed in a working dairy building; instead the CO2balance method was used as the RM which in turn had measurement errors, thereby increasing uncertainty. Using our RM, the gaseous emissions were calculated. Moreover, the emissions factors were estimated assuming that

285

the values from the summer measurements are representative for the whole year. However, due to different climate and microclimate conditions in spring, autumn, and winter the yearly emission factors might be lower. According to our study, the NH3 emission factor was 46.2 kg yr1 cow1 which agrees with that of Snell et al. (2003). Furthermore, the NH3 emission mass flow rate was 3.9 g h1 AU1 according to our results which agrees with Fiedler and Mu¨ller (2011) who stated that ammonia emission mass flow rate was in the range of 2e4 g h1 AU1. However, Adviento-Borbe et al. (2010) mentioned that the highest average NH3 emission coincided with higher environmental temperatures and that at 32  C it was 30 g d1 AU1. The average ammonia emission according to this study, subject to the uncertainties of our RM, was an average of 92.6 g d1 AU1 for the summer seasons this suggests that our value is too high since low emission values can only be achieved by reducing the emission source surfaces, by decreasing temperature and air velocity near the source, and minimising air volumetric flow rates throughout the livestock buildings (Bjorneberg et al., 2009; Blanes-Vidal, Topper, & Wheeler, 2007; Gay et al., 2003). This illustrates the conflict between the demands of animal welfare and low emissions. With new technical solutions a compromise between animal welfare and low emissions needs to be found. The 85Kr was used in minute quantities, 2 GBq per experiment, and the results of investigations of its environmental impact showed that the quantities used are safe and below the levels of natural radioactivity.

5.

Conclusions

The CO2-balance method is not generally a suitable reference measurement method to measure AERs due to the several error sources such as; calculations of metabolic energy, CO2 produced per energy unit, amount of CO2 emitted form manure and position of CO2 sampling points. The 85Kr TG used should be developed further since it delivers comparable results and is independent of the physiological changes that occur in the animals housed in the building. In contrast, the CO2-balance method depends on animal production of CO2 which varies in function of animal weight, productivity and pregnancy. It can be concluded that the sum of impulses calculation method led to better results than using the average a-values. Although there was no difference between the results from radiation counters (selected in comparison to all), considering all the readings of the radiation counters is more representative for air movement, and is easier for calculating the AER. The release of tracer gas over the manure alley produced better detection by all radiation counters emphasising the better mixing of tracer gas with air and the better distribution of tracer inside the livestock building. However, the statistical analysis carried out found no benefit in using this method, suggesting that more experiments to verify that the improvement perceived observation is correct. According to the results, it can be conclude that the best factor combinations were: (1) releasing the 85Kr tracer gas over the feeding table considering the impulses recorded by all of the radiation counters and implementing the sum method of all impulses, and (2) releasing the tracer over the feeding table and considering the impulses

286

b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 7 6 e2 8 7

recorded by selected radiation counters and implementing the average method of all impulses. The emission factors, subject to the CO2-balance RM, were 33.8, 166.6, 14504, and 8.4 kg yr1 AU1 (AU is animal unit of 500 kg) for NH3, CH4, CO2, and N2O respectively. The gaseous emissions, were 3.9, 19, 1656, and 0.96 g h1 AU1 for NH3, CH4, CO2, and N2O respectively.

Acknowledgements The authors would like to acknowledge U. Stollberg, K. Schro¨ter and D. Werner, technicians at the Department of Engineering for Livestock Management, Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Potsdam, Germany, for their technical and logistical support during the measurements. We also gratefully acknowledge the contribution of C. Loebsin and O. Tober, technicians at the Institute for Animal Production, State Institute for Agriculture and Fishery MV, Dummerstorf, Germany.

references

Aarnink, A., van Quwerkerk, E., & Verstegen, M. (1992). A mathematical model for estimating the amount and composition of slurry from fattening pigs. Livestock Production Science, 31, 133e147. Adviento-Borbe, M. A. A., Wheeler, E. F., Brown, N. E., Topper, P. A., Graves, R. E., Ishler, V. A., et al. (2010). Ammonia and greenhouse gas flux from manure in freestall barn with dairy cows on precision fed rations. Transactions of the ASABE, 53(4), 1251e1266. Albright, L. D. (1990). Environment control for animals and plants. St. Joseph, Michigan, USA: ASAE. Amon, B., & Fro¨hlich, M. (2006). Ammoniakemissionen aus frei gelu¨fteten Sta¨llen Wirtschaftsdu¨ngerlagersta¨tten fu¨r Rinder. [Ammonia emissions from naturally ventilated barns for cattle manure storage]. KTBL-Schrift, 449, 49e64, in German. ASABE Standards. (2008). Design of ventilation systems for poultry and livestock shelters. Niles Road, St. Joseph, MI, USA: ASABE. Barber, E. M., & Ogilvie, J. R. (1982). Incomplete mixing ventilated airspaces: Part I. Theoretical considerations. Canadian Agricultural Engineering, 24(1), 25e29. BfS. (1993). Radiation and radiation protection. Information brochure. Salzgitter, Germany: Federal Office for Radiation Protection (BfS). Bjorneberg, D. L., Leytem, A. B., Westermann, D. T., Griffiths, P. R., Shao, L., & Pollard, M. J. (2009). Measurements of atmospheric ammonia, methane, and nitrous oxide at a concentrated dairy production facility in southern Idaho using open-path FTIR spectrometry. Transactions of the ASABE, 52(5), 1749e1756. Blanes-Vidal, V., Topper, P. A., & Wheeler, E. F. (2007). Validation of ammonia emissions from dairy cow manure estimated with a non-steady-state, recirculation flux chamber with whole building emissions. Transactions of the ASABE, 50(2), 633e640. Brehme, G. (2000). Quantifizierung des Luftvolumenstromes in frei gelu¨fteten Rinder-sta¨llen mit Hilfe der Kompartimentalisierungsmethode zur Bestimmung umweltrelevanter Emissionsmassenstro¨me, in German (Quantification of the air flow in naturally ventilated dairy houses with the aid of the method of compartmentalization to determine emissions relevant for the environment). PhD diss., Go¨ttingen University, Germany. CIGR. (2002). Climatization of animal houses. In S. Pedersen, &

K. Sallvik (Eds.), Climatization of animal houses. Working Group Report on: Heat and moisture production at animal and house level. Denmark: DIAS, ISBN 87-88976-60-2. CIGR. (1984). Climatization of animal houses. Working Group Report on: Climatization of animal houses. Scotland, UK: International Commission of Agricultural Engineering (CIGR). Demmers, T. G. M., Phillips, V. R., Short, L. S., Burgess, L. R., Hoxey, R. P., & Wathes, C. M. (2001). Validation of ventilation rate measurement methods and the ammonia emission from naturally ventilated dairy and beef buildings in the United Kingdom. Journal of Agricultural Engineering Research, 79(1), 107e116. DIN 18910-1. (2004). Thermal insulation for closed livestock buildingsThermal insulation and ventilation forced e Part1: Principles for planning and design for closed ventilated livestock buildings. Berlin, Germany: Normenausschuss Bauwesen im DIN, Beuth Verlag. Fiedler, M., & Mu¨ller, H.-J. (2011). Emissions of ammonia and methane from a livestock building natural cross ventilation. Meteorologische Zeitschrift (Meteorological Journal), 20(1), 59e65. Gay, S. W., Schmidt, D. R., Clanton, C. J., Janni, K. A., Jacobson, L. D., & Weisberg, S. (2003). Odor, total reduced sulfur, and ammonia emissions from animal housing facilities and manure storage units in Minnesota. Transactions of the ASABE, 19(3), 347e360. Gla¨ser, M., Klich, W., & Creifelds, A. (1986). Vergleichende Untersuchungen an 85Kr und 133Xe als Tracer, in German (Comparison between 85Kr and 133Xe as tracer). Isotopenpraxis, 22(11), 411e416. Hatem, M. H. (1993). Theory of Structures and agricultural buildings and environmental Control (2nd ed.). Egypt: Faculty of Agriculture, Cairo University. Hellickson, M. A., & Walker, J. N. (1983). Ventilation of agricultural Structures. St. Joseph, Michigan, USA: ASAE. Keck, M., Schrade, S., & Za¨hner, M. (2006). Minderungsmaßnahmen in der Milchviehhaltung, in German (Mitigation measures in the dairy farming). KTBL-Schrift, 449, 211e227. Kittas, C., Boulard, T., Mermier, M., & Papadakis, G. (1996). Wind induced air exchange rates in a greenhouse tunnel with continuous side openings. Journal of Agricultural Engineering Research, 65(1), 37e49. LLBB. (2005). Jahresbericht Verbraucherschutz und Gesundheitsschutz fu¨r Mensch und Tier: Umweltschutz und nachhaltiger Ressourcenschutz. [Annual Report on Consumer and health protection for people and animals: Environmental protection and sustainable resource protection]. Berlin, Germany: BerlinBrandenburg State Laboratory. in German. Lung, T., Mu¨ller, H. J., Gla¨ser, M., & Mo¨ller, B. (2002). Measurements and modelling of full-scale concentration fluctuations: openfield experiments using krypton-85 and tetrahydrothiophene as tracers. Agrartechnische Forschung, 8(1/3), 5e15. Madsen, J., Bjerg, B. S., Hvelplund, T., Weisbjerg, M. R., & Lund, P. (2010). Methane and carbon dioxide ratio in excreted air for quantification of the methane production from ruminants. Livestock Science, 129(2010), 223e227. Monteny, G. -J. (2000). Modeling of ammonia emissions from dairy cow houses. PhD dissertation Wageningen University and Research Centre, Wageningen, Netherlands. Mosquera, J., Monteny, G. J., & Erisman, J. W. (2005). Overview and assessment of techniques to measure ammonia emissions from animal houses: the case of the Netherlands. Environmental Pollution, 135(2005), 381e388. Mu¨ller, H. J., & Mo¨ller, B. (1998). The further development of air exchange measurement techniques using tracer gases. Landtechnik, 53(5), 326e327. Mu¨ller, H.-J., Krause, K.-H., & Grimm, E. (2001). Geruchsemissionen und eimmissionen aus der Rinderhaltung. [Odour emissions and immissions from livestock farming]. KTBL-Schrift, 388, 105e112, in German.

b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 7 6 e2 8 7

Ngwabie, N. M., Jeppsson, K.-H., Nimmermark, S., Swensson, C., & Gustafsson, G. (2009). Multi-location measurements of greenhouse gases and emission rates of methane and ammonia from a naturally-ventilated barn for dairy cows. Biosystems Engineering, 103(2009), 68e77. Okuyama, H., Onishi, Y., Tanabe, S.-I., & Kashihara, S. (2009). Statistical data analysis method for multizonal airflow measurement using multiple kinds of perfluorocarbon tracer gas. Building and Environment, 44(3), 546e557. Pedersen, S., Takai, H., Johnsen, O., Metz, J., Groot Koerkamp, P., Uenk, G., et al. (1998). A comparison of three balance methods for calculating ventilation rates in livestock buildings. Journal of Agricultural Engineering Research, 70, 25e37. Pedersen, S., Blanes-Vidal, V., Joergensen, H., Chwalibog, A., Haeussermann, A., Heetkamp, M. J. W., et al. (2008). Carbon dioxide production in animal houses: a literature reviewIn Agricultural Engineering International: CIGR Ejournal, Manuscript BC 08 008, Vol. X. December, 2008. Pinares-Patino, C. S., & Clark, H. (2008). Reliability of the sulfur hexafluoride tracer technique for methane emission measurement from individual animals: an overview. Australian Journal of Experimental Agriculture, 48(1e2), 223e229. Ponchant, P., Hassouna, M., Ehrlacher, A., Aubert, C., Amand, G., Leleu, C., et al. (2008). Application and validation of a simplified measurement method of gaseous emissions in naturally ventilated livestock buildings. TeMA - Techniques et Marches Avicoles, 6, 4e10. Sallvik, K. (1999). Environment for animals. In E. Bartali, A. Jongebreur, & D. Moffitt (Eds.), CIGR Handbook of agricultural Engineering, Vol. 2 (pp. 31e88). St. Joseph, Michigan, USA: ASAE. Schneider, B. (1988). Computergestu¨tzte kontinuierliche Erfassung der Wa¨rme-, Wasserdampf- und Kohlendioxidproduktion in Nutztiersta¨llen, in German (Computer-based continuous recording of heat, water vapor, and carbon dioxide production

287

in livestock barns). PhD dissertation University of Hohenheim, Germany. Schneider, T., Buscher, W., & Wallenfang, O. (2005). Validation of the tracer gas method for air volume flow measurement. Landtechnik, 60(6), 344e345. Scholtens, R., Dore, C. J., Jones, B. M. R., Lee, D. S., & Phillips, V. R. (2004). Measuring ammonia emission rates from livestock buildings and manure stores - part 1: development and validation of external tracer ratio, internal tracer ratio and passive flux sampling methods. Atmospheric Environment, 38(19), 3003e3015. Sherman, M. H. (1989). On the estimation of multizone ventilation rates from tracer gas measurements. Building and Environment, 24(4), 355e362. Snell, H., Seipelt, F., & van den Weghe, H. (2003). Ventilation rates and gaseous emissions from naturally ventilated dairy houses. Biosystems Engineering, 86(1), 67e73. ¨ zcan, S., Vranken, E., Van Buggenhout, S., Van Brecht, A., Eren O Van Malcot, W., & Berckmans, D. (2009). Influence of sampling positions on accuracy of tracer gas measurements in ventilated spaces. Biosystems Engineering, 104(2009), 216e223. VEB. (1972). Encyclopedia “health”. Leipzig, Germany: VEB Bibliography Institute of Leipzig. Von Bobrutzki, K., Braban, C. F., Famulari, D., Jones, S. K., Blackall, T., Smith, T. E. L., et al. (2010). Field inter-comparison of eleven atmospheric ammonia measurement techniques. Atmospheric Measurements Techniques, 3, 91e112. Von Bobrutzki, K., Mu¨ller, H.-J., & Scherer, D. (2011). Factors affecting the ammonia content in the air surrounding a broiler farm. Biosystems Engineering, 108, 322e333. Xin, H., Li, H., Burns, R. T., Gates, R. S., Overhults, D. G., & Earnest, J. W. (2009). Use of CO2 concentration difference or CO2 balance to assess ventilation rate of broiler houses. Transactions of the ASABE, 52(4), 1353e1361.